Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

h, w = [int(i) - 1 for i in input().split()]
ans = 0
maze = []
for i in range(h + 1):
    s = list(input())
    maze.append(s)
    ans += s.count(".")

pos = deque([[0, 0, 0]])

while pos:
    y, x, b = pos.popleft()
    for ny, nx in [[1, 0], [-1, 0], [0, 1], [0, -1]]:
        if y + ny == h and x + nx == w:
            print(ans - b - 2)
            exit()
        if 0 <= y + ny <= h and 0 <= x + nx <= w and maze[y + ny][x + nx] == ".":
            pos.append([y + ny, x + nx, b + 1])
            maze[y + ny][x + nx] = "#"
print(-1)